Pneumatic tool



May 21, 1929. F. M. SLATER PNEUMATIC TOOL Filed Sept. 50, 1927 w T QQVNR m m N B v g HNa KHQ N% 2 R. aw f/z? A w Patented May 21, 1929.

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T Iilt'GEESDLL- RAND COM-- CORPOEATIOJ OF NEW" JERSEY.

PNEUMATEC TOOL.

Application filed September This invention relates to pneumatic tools,but more particularly to pneumatic tools of the hammer type in which thedrill steel or its equivalent extends into the front end of the cylinderand in its operative position, limits the forward travel of the hammerpiston.

One object of the invention is to prevent the hammer piston fromstriking against the forward extremity of the cylinder whenever theworking implement is permitted to with draw from its normal operativeposition due to the relaxation of the manual pressure necessary formaintaining the said working implement within the range of the blows ofthe hammer piston.

Other objects -will be in part obvious and in part pointed outhereinafter.

In the drawings illustrating a practical application of the invention,

Figure 1 is a longitudinal vertical section of a pneumatic toolconstructed in accord-' ance with the practice of the invention, and

Figure 2 is a view similar to Figure 1 showing the working. implementwithdrawn from its normal operative position thusenabling the hammerpiston to advance be yond its forward limiting position and cover thefront inlet port to the cylinder.

Referring more particularly to the drawings, A designates a cylinder ofa pneumatic tool having free exhaust ports B which are controlled by apiston C reciprocable in a piston chamber A of the cylinder A. In thefront end of the cylinder A is a bore 1) in which is disposed a bushing,E. A working implement F, such as a coal pick or drill steel, is guidedby the bushing E and has a shank G which normally extends into the frontendiof the piston chamber a substantial distance to receive the blows ofthe hammer piston O.

The means which serves to limit the distance which the shank G mayextend into the piston chamber A consists of a collar H on the workingimplement F, preferably of slightly larger diameter than the bushing);E, to enable said collar H to abut against the front end of the cylinderA.

The collar H further acts as a means for preventing complete ejection ofthe working implement F from the cylinder A. To this end said collar Hmay contact with an end wall J of a cap K threaded on the front end ofthe cylinder A, said cap having a bore 30, 1927. Serial No. 223,0d6.

L in its front end to enable the working implement ll to extend slidablytherethrough.

The distribution of pressure fluid to the ends of the piston chamber maybe effected by any suitable and well. known means. The means shown inthe drawings for this purpose comprise a valve mechanism consisting of aplate type oscillatory valve 0 pivoted on a pin P seated in a valve seatQ on the rearward end of the cylinder A. y The valve seat Q; is held inoperative position by a back head R having a hood S threaded on therearward end of the cylinder 21. A valve chamber T in the back head itand in which the val\ c Q is disposed in constant communication with asuitable source of pressure fluid supply (not shown) through a passage Uopening at its inner cud into an annular chamber'V above the valve 0.

Leading: from one side of the valve 01121131 her '1 to the front endofthe piston chamber is an inlet passage iV, the inlet port X of which ispreferably spaced a substantial distance from the front end of thepiston chamher A. The admission of pressure fluid to the rearward endofthe cylinder A is effected through an inlet passage Y in the valveseat Q. v r

In order to prevent the formation of high compression in the front endof the piston chamber A, said piston chamber is provided with acompression relief passage Z which opens into the piston chamber at asuitable point between the exhaust port B and the front end of thepiston chamber and leads directly to the atmosphere.

In accordance with the present invention, the piston C is provided withan annular groove .6 so located on the piston C that when said pistonoccupies a position in the extreme front-end of the piston chamber A,said groove Z) will lie in advance of the inlet port X. The piston,however, may only assume this-position. when the working implement F ispermitted to withdraw from the range of the blows of the-hammer piston,since during normal drilling, the shank of the working inmleinent F willextend into the piston chamber a distance suiiicient to prevent completecovering of the inlet port X by the piston C.

The function of the annular groove Z) is to interceptany pressure fluidwhich would otherwise leak along the piston into the front end of tliepiston chamber when the in the piston chamber. The groove 0 is of suchlength that when the piston G occupies the extreme forward position, therearward end of the groove 0 will be uncovered by the corresponding endof the piston over which the pressure fluid may pass into the pistonchamber rearwardly of the pistonC and escape through the compressionrelief passage and the exhaust ports B As will be observed the annulargroove 0 and the longitudinal groove 0 are solocated andof suchproportions that it will be impossible for live pressure fluid to escapefrom'the inlet port X through these channels to the atmosphere, since,while the annular groove Z) is in registry with the inlet port X, therearward end of the longitudinal groove 0 will still be covered by therearward end of the piston C on both the forward and rearward strokes ofthe piston.

The front end of the pistonrC carries a reduced projection d whichstrikes against the shank G of the working implement F and is preferablyof slightly smaller diameter than a bore 6 in the bushing E. In this waytherewill be sufficient clearance between the projection d and the bore6 to permit the exhaust of compression from the front end of the pistonchamber A to the atmosphere through passages 7 in the bushing E and thefront end of the cylinder A. During the normal operation of the device,the working implement F will of course project into the piston chamber Ato the full extent permitted by the collar H and,

- aspreviously explained, the working implement will prevent the pistonC from overrunning the inlet port X. If, however, the operatorcarelessly relaxes the manual pressure necessary for holding the workingimplement properly to the work, the piston C will be forced to theextreme forward end of thepiston chamber A. In such case the inlet'portX will be covered by the piston and the'admission of pressure fluid tothe front end of the piston chamber will be prevented.

During the time that the'piston'G occupics the extreme forwardposition'referred to, pressure fluid will of course leak past the pistonin opposite directions, that flowing rearwardly along the piston. willescape to the atmosphere through the exhaust ports B. The-pressure fluidleaking in a forwardly direction will be intercepted by the annulargroove 6 in the piston and conveyed thereby to the longitudinal groovec,The pressure fluid thence passes through the groove 0 into the pistonchamber rearwardly of the piston and to the atmosphere through theexhaust ports B.

Whenever the workin im )lement F is permitted to withdraw from itsnormal operative position in the cylinder, the movement of the pistonwill be quickly arrested and the piston will remain stationary until itis again moved rearwardly by the working implementto uncover the inletport X.

I claim: 7

1. A pneumatic tool. comprising a cylinder having a piston chamber andinlet and exhaust ports, a work implementextending normally asubstantial distance into the piston chamber, a hammer pistonreciprocable in the piston chamber having a groove for interceptingpressure fluid 'leaking past the piston toward the front endofthecylinder whenever the piston passes beyond its normal limitingposition, and a groove in the piston chamber for conveying such pressurefluid past the end of the'piston from whence it may pass through theexhaust port to the atmosphere. 7

' 2. A pneumatictool comprising a cylinder having a piston chamberand-inlet and'exhaust ports, a hammer piston reciprocable in the pistonchamber, a working implement normally extending into the piston chambersufiicient distance to prevent'the piston from over-running the inletport, an annular groove in the piston for intercepting pressure fluidleaking along the piston toward the front end of the cylinder wheneverthe working implement is withdrawn from its normal operative position,thuspermitting the piston to overrun the inlet port, and a groove in thepiston chamber registering with the annular groove for conveying theintercepted pressure fluid past the rearward end of the piston fromwhence it may es cape through the exhaust port to the atmosphere. U

In testimony whereof I have'signed this specification.

FRED S ATER

